An internal combustion engine which is liquid-cooled may include at least one coolant jacket positioned in the cylinder head and/or block of the engine. Coolant may be supplied to an inlet of the coolant jacket, circulated through the cylinder head and/or block thereby cooling the engine, and expelled via an outlet of the coolant jacket at which point the heated coolant may be supplied to a heat exchanger where heat may be extracted from the coolant and expelled to the ambient environment or another location such as a passenger compartment. Liquid cooling is being increasingly implemented in internal combustion engines as the use of superchargers and turbochargers has become more prevalent, and as engine components (e.g., exhaust manifolds) are being increasingly integrated into the cylinder head and/or block to achieve dense packaging. Generally, the cylinder head is more thermally loaded than the cylinder block, due to its relatively lower mass, possession of lines which conduct hot exhaust gas, and the relatively longer exposure to high temperatures of its combustion chamber walls compared to the cylinders disposed in the cylinder block. As such, different cooling strategies respective to the cylinder head and block may be sought. For example, it may be sought to cool the cylinder head more thoroughly than the block as operation of the valve actuation system may be optimized at relatively lower temperatures by avoiding mixed friction in its bearings, whereas friction losses between cylinder liners and pistons may be minimized by maintaining the cylinder block at relatively higher temperatures.
German pat. app. no. DE 100 61 546 A1 describes a cooling system for an internal combustion engine which is cooled via a liquid coolant. To control the quantities of coolant which flow through coolant lines of a cylinder head and through coolant lines of a cylinder block, dedicated thermostat valves are positioned downstream of the cylinder head and block. Here, the thermostat valve of the cylinder head has a lower opening temperature than the thermostat valve of the cylinder block. Here, a thermostat valve with an invariant, component-specific operating temperature is selected to be suitable for all load states and therefore have an opening temperature configured for high loads, which is comparatively low and leads to relatively low coolant temperatures even in part-load operation. A low coolant temperature in part-load operation correlates with a relatively large temperature difference between the coolant and the component.
The inventors herein have recognized several issues with such an approach. With such a cooling system, a relatively large amount of heat transfer occurs at low and medium loads, which reduces efficiency during part-load operation. Further, two thermostat valves are utilized, increasing cost, complexity of control routines, weight, and packaging space.
To address these issues, systems providing demand-based independent cooling of a cylinder head and block in an internal combustion engine are provided.
In one example, an internal combustion engine includes a cylinder head, a cylinder block coupled to the cylinder head, a first return line fluidically coupled to the cylinder head and to a coolant valve and including a heat exchanger configured to remove heat from coolant, a second return line fluidically coupled to the cylinder block and to the coolant valve, a bypass line branching off from the first return line and fluidically coupled to the coolant valve, and an originating supply line fluidically coupled to the cylinder head, the cylinder block, and the coolant valve, the originating supply line including a pump configured to supply coolant. The coolant valve is configured to control coolant flow through the first return line, the second return line, the bypass line, and the originating supply line via rotational selection of one of a plurality of working positions.
In this way, independent cooling of a cylinder head and block may be facilitated based on demand, including scenarios in which maximum extraction of heat from an engine is not desired.